# Atherosclerosis --- **Atherosclerosis** is a chronic, progressive, inflammatory [[blood vessels|vascular disease]] that is characterized by the deposition of **atheroma** or **plaque** on the inner walls of [[blood vessels]]. It can be found in the large and medium arteries, for example the aorta and the large vessels that supply the brain. Atherosclerois can also be found in the coronary coronary arteries and is called [[coronary artery disease]]. It can happen anywhere along these vessels, but it is most common where there are branches or curves in the vessel, which cause turbulent blood flow. The exact triggering condition in unknown, but it begins when the inner lining of the blood vessels—the [[epithelial tissue|endothelium]]—is chronically injured or inflammed. Under chronic inflammation, the endothelium stops producing antiinflammatory chemicals. Conditions that can cause that are commonly: - [[hypertension]] - [[smoking]] - [[animal virus|viral]] infection - high [[cholesterol]] levels - [[hyperglycemia]] ![[atherosclerosis.png]] ## Formation of Aetheroma **Atheroma** is the name for the large plaque in the vessel walls. This is formed over the course of time as the condition worsens. The first phase, as the endothelium is inflammed it allows [[macrophages]] to enter into it and take up residence. They eat up [[lipoprotein|LDL]] in the blood and just sort of hang onto it. This turns them into **foam cells** as they take on a puffed up, foamy appearance under a microscope. As foam cells accumulate, a **fatty streak** is formed. This is made up of the accumulated foam cells as well as other stuff that has accumulated. They are flat, thick yellow lesions that become larger and larger as time goes on, protuding into the lumen of the vessel. Over time (decades) the fatty streak builds up and hardens into something called a **fibrous atheromatous plaque**. This is where the real trouble begins. These plaques have a thick, fibrous cap on the top of them that effectively narrow the lumen of the vessel and reduce blood flow. This is particularly dangerous in the [[coronary circulation|coronary arteries]] because it then blocks bloodflow to the [[cardiac muscle|myocardium]] itself. In some cases, the atheromatous plaques develop into **atheromas**, which are calcified lesions that can cause hemorrhage, surface ulcerations and scar tissue deposits. In addition can cause sluggish bloodflow, which is ideal for causing a [[thrombus|thrombosis]]. ### Stable & Unstable Plaque The plaque can form into either stable, or unstable plaque. Both are bad, but **stable plaque** is covered with a thick fibrous cap. It still occludes part of the bloodflow, but it is predictable. In the heart this type of plaque leads to [[angina|stable angina]]. **Unstable plaque** has a thin fibrous cap that has a tendancy to rupture, which causes clots and [[thrombus]] formation. Additionally, as the rupture heals it can narrow the artery even more. This type of plaque in the heart can lead to [[angina|unstable angina]] or [[myocardial infarction|MI]] if present in the [[coronary circulation|coronary arteries]]. ___